The wiring in most existing homes generally takes the form of a four-wire set, in which one pair of wires carries one telephone channel, and the other pair, if desired, carries a second channel.
Other types of buildings, such as commercial office buildings, contain similar telephone cable, which is used not only to support telephone service, as in a residence, but also to support a data network, in which computers communicate with each other. However, using the telephone cable to support the data network requires additional equipment, which may be expensive, and may require a system administrator for support.
U.S. Pat. No. 4,578,540, issued on Mar. 25, 1986, to Borg, Halas, Mattes, McLear, and White and entitled xe2x80x9cTelecommunications Systems,xe2x80x9d discloses a controller which is interposed between an incoming telephone line and the telephones to which the incoming line provides service. The arrangement described by Borg, et al., (hereinafter, xe2x80x9cBorgxe2x80x9d) is shown in FIG. 1.
As seen in FIG. 1, Borg""s system contains a ring detector 140 for detecting a ring signal provided by the telephone central office. When a ring signal is detected, a data processor 110 is informed of the ring signal. The processor 110 actuates a ring generator 119 which issues a ring signal to all telephones connected to the controller. These telephones are indicated by the phrase xe2x80x9cTOWARD EXTENSION TELEPHONESxe2x80x9d located at the upper right part of FIG. 1.
When one of these telephones answers the ring, as by going off-hook, for example, that fact is detected by a line-current detector 118. In response, the processor 110 closes relays SHM1, SHM2 (both at the upper left), and relays COM and PHM (both just below the phrase xe2x80x9cFIG. 1xe2x80x9d). At this time, the off-hook-telephone is now connected to the incoming call.
The Borg arrangement provides a number of desirable features. For example, a user of the controller can store telephone numbers in a memory, labeled RAM 111. When an incoming call is received, the processor 110 answers the call with a message starting xe2x80x9cThis is the Jones residence. Please dial your telephone number to leave a message.xe2x80x9d When the caller enters the telephone number, the processor 110 compares the number with those in RAM 111. If no match is found, the processor does not actuate the ring generator 119, and the telephones controlled by the controller do not ring. The incoming call is blocked. This feature prevents receipt of unwanted telephone calls.
Moreover, xe2x80x9cdistinctive ringingxe2x80x9d can be implemented. In addition to storing the telephone numbers as described immediately above, a user can associate data which indicates a ringing pattern with each telephone number. When an incoming call is received and the caller enters a telephone number, the processor 110 looks for the number in the RAM 111. When the number is found, the processor 110 looks for the ring pattern associated with that number, and actuates ring generator 119 accordingly. For example, a call from Adams may result in the ring pattern of xe2x80x9cLONG, SHORT, LONG.xe2x80x9d xe2x80x9cDistinctive ringingxe2x80x9d can be used in connection with an intercom mode, which is provided by the controller. A person takes a telephone controlled by the controller off-hook. The processor detects the off-hook status, through line-current detector 118, and waits for a signal. If the person presses the xe2x80x9c#xe2x80x9d key of the telephone, the processor then knows that the person wishes to place a call in intercom mode. The processor then waits for a key-press sequence, which identifies a recipient of the intercom call. When the key-press sequence is received, the processor looks up a ring sequence associated with the sequence, in RAM 111. The processor rings all telephones with the ring sequence, thus summoning the person who has been assigned that sequence.
The controller can issue Dual-Tone, Multi-Frequency (DTMF) signals, using ADDRESS OR COMMAND SIGNAL GENERATOR 115. These signals can be issued to either the telephone central office or the extension telephone sets. DTMF signals are those generated by the keys of a standard keypad telephone. The DTMF signaling convention is described in Reference Data for Engineers: Radio Electronics, Computers and Communications, E. C. Jordan, editor, 7th edition, 1985, Howard K. Sams and Co., page 38-16. Finally, the processor 110 can control a PERIPHERAL DEVICE INTERFACE 114. In general, this INTERFACE 114 is a data port which can be used to communicate with numerous devices, such as burglar alarms, fire alarms, utility meter-reading equipment, and so on.
As indicated above, the Borg arrangement provides a number of significant advantages. Disadvantageously, however, Borg does not fully utilize the bandwidth available in the telephone lines supplied to his device.
According to the present invention, advances are made in the prior art by a system in which two pairs of telephone cable are used to support four communication channels: two voice channels and two data channels. A controller can route data and voice calls among devices wishing to use the channels.